1. Field of the Invention
The present invention relates to an optical disc reader that reads data recorded on optical discs such as CDs, DVDs, and Blu-ray discs (BDs).
2. Description of the Related Art
Optical disc readers read data recorded on an optical disc by focusing a light beam onto the optical disc and receiving the light reflected from the optical disc while rotating the optical disc. For reading data recorded on an optical disc, such an optical disc reader operates as shown in FIG. 6.
First, the optical disc reader performs a focusing operation for causing the focal point of the light beam to be on a data recording layer in the optical disc (S91). Subsequently, the optical disc reader performs tracking error (TE) signal conditioning to amplify a TE signal (S92), and then performs a tracking operation for causing the focal point of the light beam to be on a data recording track on the optical disc (S93).
Then, the optical disc reader determines whether or not the servo status is OK (S94). More particularly, it determines whether or not the focusing operation has been performed properly and focusing servo (for keeping the focal point of the light beam on the data recording layer in the optical disc) is in normal operation, and whether or not the tracking operation has been performed properly and tracking servo (for keeping the focal point of the light beam on the data recording track on the optical disc) is in normal operation.
If the servo status is OK (i.e., if the focusing servo and tracking servo are in normal operation) (YES at S94), the optical disc reader starts the read operation to read data recorded on the optical disc (S95).
On the other hand, if the servo status is not OK (i.e., if the focusing servo is not in normal operation or if the tracking servo is not in normal operation) (NO at S94), the optical disc reader performs a recovery operation by repeating the process from the above step S91. Further, after the start of the read operation, if the read operation is not OK (i.e., if data recorded on the optical disc cannot be read out normally) (NO at S96), the optical disc reader also performs the recovery operation by repeating the process from the above step S91.
Japanese Laid-open Patent Publication No. 2005-38542 discloses an optical disc reader designed to reduce the time of focus search by first performing a preliminary focus search to detect search driving voltages at the times of peak and bottom in a focus error signal and then performing an actual focus search within the range between the search driving voltages detected at the times of peak and bottom. Japanese Laid-open Patent Publication No. HEI 9-330554 discloses an optical disc reader designed to determine the type of an optical disc based on a tracking error signal. Further, Japanese Laid-open Patent Publication No. 2006-31885 discloses an optical disc reader designed to determine the type of an optical disc based on a focus drive value at the time when the focal point reaches a recording surface during a focus search or based on a focus drive value in an in-focus condition.
Typically, optical discs comprise a transparent substrate layer, data recording layers formed on the substrate layer, and a protective layer formed on the data recording layers. From the substrate layer side of an optical disc, an optical disc reader focuses a light beam onto the optical disc. Therefore, in the focusing operation, the light beam may not be properly focused (on a data recording layer in the optical disc) but may be focused on the surface of the optical disc (surface of the substrate layer) or other improper position.
In the above described conventional optical disc reader, when the focusing operation at the step S91 has not been performed properly, the tracking operation at the step S93 is not performed properly so that the tracking servo operation is not performed normally. Even if the tracking servo operation is performed normally, data recorded on the optical disc cannot be read out properly in the read operation at the step S95. Thus, when the focusing operation at the step S91 has not been performed properly, the result at the step S94 or the step S96 would be NO, which causes the optical disc reader to perform the recovery operation.
In other words, when the focusing operation has not been performed properly, the conventional optical disc reader still performs the tracking operation although the light beam is not properly focused on the data recording layer, and thereafter performs the recovery operation. This will increase the time taken for the recovery operation to be performed after the focusing operation has been performed improperly. This problem cannot be solved even with the techniques disclosed in the above mentioned patent documents.